Chapter 48

The adsorptive capacity of charcoal has been documented since the time of Hippocrates and has been known for centuries. Two independent researchers were responsible for its wide acceptance in the early nineteenth century when each of them performed a demonstration of its effectiveness by ingesting lethal doses of strychnine and arsenic, respectively, followed by charcoal. Both of them survived. The twentieth century has seen charcoal come into wide medical use as further investigation showed its effectiveness to adsorb a wide variety of compounds.1

Charcoal is produced by the distillation of the pyrolysis products of vegetable matter or wood. It works by directly adsorbing toxins via a variety of chemical binding properties and thereby preventing the toxins from being absorbed from the gastrointestinal tract. Improvement in the adsorptive capability of charcoal is achieved by heating it to a temperature of 900 Celsius and washing it in a stream of carbon dioxide gas or steam. This process is called activation and creates an internal pore structure that increases the surface area from 2 to 4 square meters per gram to greater than 2000 square meters per gram.2 A typical dose of 50 grams of activated charcoal has the surface area of ten football fields. Charcoal is not absorbed from the intestinal lumen and is not modified by the numerous enzymes and proteins that aid in the digestion of food. It passes through the intestinal tract and is expelled from the anus as a sticky black substance.

Some charcoal preparations contain sorbitol. This substance is used as a flavoring agent to make food, drinks, and medications more palatable. Sorbitol is also used as a hyperosmotic laxative agent. It is poorly absorbed from the gastrointestinal tract and converted into fructose by the liver. Its limited absorption into the body results in an increased volume of water secreted into the intestine and an increased intraluminal pressure stimulating a catharsis.

A second mechanism of charcoal’s action involves the patient’s enteroenteral and enterohepatic circulation. A diffusion gradient is created in the intestine due to the huge adsorptive ability of charcoal to bind free drug or free toxin. This makes the toxin concentration in the intestine effectively zero. The intestinal wall works as a semipermeable membrane allowing the drug or toxin to diffuse from the capillaries into the lumen of the intestine. The charcoal cannot cross the wall of the intestine and is not absorbed. This diffusion gradient draws the drug or toxin into the intestine and allows the activated charcoal to trap it, maintaining the gradient.3 This mechanism essentially dialyzes the blood in the capillaries of the intestinal circulation. Many drugs, toxins, and their metabolites are secreted into the bile and back into the intestinal lumen. Activated charcoal will adsorb these substances and prevent them from once again entering the systemic circulation.

Activated charcoal is effective for the majority of commonly ingested substances and is considered the agent of ...

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